Advances in medicine have dramatically increased pediatric cancer survival rates; 80% of children diagnosed with cancer will survive beyond five years. This victory carries with it new agendas for research, as attention shifts to the mechanisms underlying the quality of life of survivors. Quality of life includes div aspects of functioning including functional ability, psychological functioning, and disease- and treatment-related symptoms. Understanding these processes demands integrative, biobehavioral models of functioning in the cancer context. Unfortunately, development and testing of competing models in pediatrics has lagged behind research focusing on adults and animals. The proposed research is designed to be a first step in identifying biological and behavioral mechanisms by which risk and protective factors influence children's health. Evidence from both adult and animal studies indicates a relationship between stress and immune function, with much of the current focus on cytokines, the key proteins in the immune cascade. Broad sociodemographic and life stress (e.g., SES, life events), biological factors (e.g., age at disease onset), health behaviors (e.g., sleep, diet, exercise), and psychosocial processes (e.g., coping, meaning making) interact to influence mental health and immunologic factors in turn influences disease processes (e.g., progression, recovery, quality of life). For example, adult and animal research demonstrates that chronic and acute stress can compromise immune function, which in turn fosters poorer cancer outcomes. Yet, this research has not been translated to children with cancer, despite evidenced links between stress and biological, psychological, and relationship system functioning in other contexts. The two proposed studies are each short-term longitudinal studies of the mediating and moderating relationships among sociodemographic stress and family protective processes as they influence child health outcomes. In the first study, the association of infants' immune function with stressful family life events and maternal sensitive care giving is examined. In the second study, the association of pediatric cancer patients' immune and mental health function with sociodemographic stress and (1) child secure appraisals and health behaviors, and (2) caregiver and family protective processes. The public health significance of this work lies in its potential to highlight multiple, individual- and famil-level points of intervention within populations of vulnerable, immunocompromised children.